Cell Division

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Cell Division
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Recall from Cycle 1

• There are two types of reproduction
• Asexual Only takes one parent
• - No fusion of gametes (sperm and ova)
  - Daughter cells are an exact copy
  of parent cell
• 2. Sexual - Takes two parents
• - A fusion of two gametes (sperm ova)
• - Daughter cells are genetically diverse
  from parent cell

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• Cell division is the process by which cells
  reproduce.
• Cell division enables
• Reproduction
• 2. Growth of organisms.
• 3. Repair of organisms.

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• Reproductive Cells
• - cells that produce gametes (sperm and ova).
• - Sexual reproduction
• Somatic Cells
• - all non-reproductive cells
• - Asexual reproduction

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• Somatic cells contain 23 pairs of chromosomes for
  a total of 46 chromosomes.
• (23 pairs) 23 x 2 46
• Reproductive cells contain a total of 23
  chromosomes. NOT 23 PAIRS!

46 chromosomes
23 chromosomes
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Mitosis Somatic cells (Asexual Reproduction)

• Mitosis is the process of forming identical
  daughter cells by replicating and dividing the
  original parent cell.
• making a cellular Xerox.

• Most cells in the human body are produced by
  mitosis.
• Ex. - Skin cells
• - Muscle Cells
• - Etc.

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• Mitosis Somatic cells (Asexual Reproduction)

Parent Cell
Daughter Cell (exact copy of parent
cell)
Daughter Cell (exact copy of parent
cell)
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Phases of Mitosis
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2
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3
4
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Phases of Mitosis

1. Interphase The cell grows and duplicates
   its genetic material
2. Prophase Pairs of chromosomes form. The
   nuclear envelope is disappearing.
3. Metaphase the chromosome pairs line up in
   the middle of the cell.  

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• 4. Anaphase Each chromosome splits and
  moves to opposite poles (sides) of the
  cell.
• 5. Telophase a new cell membrane forms
  and pinches inward dividing the cell into
  two equal parts.
• The cycle starts again with the new cells

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Another Look at Mitosis
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Meiosis Reproductive cells(Sexual Reproduction)

• Meiosis is a 2-step process that reduces the
  number of chromosomes by half during gamete
  formation.
• Gamete sperm and ovum (egg)

Meiosis I
Meiosis II
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Meiosis Reproductive cells(Sexual Reproduction)
Parent Cell
Gamete
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• Then, fertilization during intercourse produces
  a cell with the full 46 chromosomes.
• ( ½ from mom ½ from dad)

Mother Father Baby
23 chromosomes
23 chromosomes
46 chromosomes


(egg) (sperm)